Revert "Disable flaky PaintCanvasVideoRendererTest tests"

This reverts commit 6f601682.

Reason for revert: The CL that caused these tests to fail has been
reverted. Reenabling these tests to confirm issue is resolved. Link
to other revert: crrev.com/c/2212560

Original change's description:
> Disable flaky PaintCanvasVideoRendererTest tests
>
> No change to production logic. This disables flaky tests.
>
> TBR=dalecurtis@chromium.org
>
> Bug: 1085516
> Test: None
> Change-Id: I1eb617e7ca8dcb1edce3ebffdb2fa17bb566a650
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2212754
> Reviewed-by: Nate Fischer <ntfschr@chromium.org>
> Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
> Commit-Queue: Nate Fischer <ntfschr@chromium.org>
> Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#771175}

TBR=dalecurtis@chromium.org,ntfschr@chromium.org

Change-Id: I07e8cb64f3c92f113837c476b7ffc2122c4eba45
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1085516
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2212994
Commit-Queue: Nathan Zabriskie <nazabris@microsoft.com>
Reviewed-by: Nathan Zabriskie <nazabris@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#771243}

media/renderers/paint_canvas_video_renderer_unittest.cc

@@ -1306,8 +1306,7 @@ class PaintCanvasVideoRendererWithGLTest : public PaintCanvasVideoRendererTest {
   scoped_refptr<viz::TestInProcessContextProvider> destination_context_;
 };
 
-TEST_F(PaintCanvasVideoRendererWithGLTest,
-       DISABLED_CopyVideoFrameYUVDataToGLTexture) {
+TEST_F(PaintCanvasVideoRendererWithGLTest, CopyVideoFrameYUVDataToGLTexture) {
   auto* destination_gl = destination_context_->ContextGL();
   DCHECK(destination_gl);
   GLenum target = GL_TEXTURE_2D;
@@ -1339,7 +1338,7 @@ TEST_F(PaintCanvasVideoRendererWithGLTest,
 }
 
 TEST_F(PaintCanvasVideoRendererWithGLTest,
-       DISABLED_CopyVideoFrameYUVDataToGLTexture_FlipY) {
+       CopyVideoFrameYUVDataToGLTexture_FlipY) {
   auto* destination_gl = destination_context_->ContextGL();
   DCHECK(destination_gl);
   GLenum target = GL_TEXTURE_2D;